1. Field of the Invention
The present invention relates to a relay server that enables client terminals connected to local area networks (LANs) to communicate with one another beyond a wide area network (WAN).
2. Description of the Related Art
By using a virtual private network (VPN), a client terminal can communicate with another client terminal remotely located across a WAN. However, it is difficult for the VPN to construct a network that has expandability and flexibility.
A relay communication system disclosed in Japanese Patent Laid-Open Publication No. 2008-129991 can construct a network that appears as if remote LANs are directly connected to one another, in a similar way to a VPN. This relay communication system has better expandability and flexibility than a general VPN in that it is possible to dynamically change the group relationship among the LANs, and so on.
In the relay communication system disclosed in Japanese Patent Laid-Open Publication No. 2008-129991, each relay server shares identification information of the client terminals connected to each LAN, thus enabling communication among the client terminals. Specifically, association information between identification information of the relay servers and identification information of the client terminals is shared by the entire network, thus making it possible for the relay servers to relay communication packets among the client terminals.